1. Field of the Invention
This invention relates in general to electronic reproduction technology and in particular to methods and apparatus for producing color images particularly from copy masters for multi-color printing.
2. Description of the Prior Art
In the reproduction technology for multi-color or process printing, copy masters are made from original masters before the production of the color separations. The copy masters are color corrected relative to the original masters and are adapted in density range, in other words, are standardized in terms of density and enlarged to the final format under given conditions. The copy masters can be opaque copy masters which chromatically correspond to the printed product which is to be later produced in the highest possible degree and are employed as print-committing copy masters which, for example, are examined by the client so that he can evaluate them and give final authorization for printing or they may be employed as proofs for the quality control in multi-color or process printing. The copy masters can also be transparency copy masters such as, for example, duplicate transparencies produced from original transparencies which also can be utilized for a reproduction supervision. The color images to be produced can also, however, be a matter of simple color copies of color picture originals that are prepared by businesses for developing or reproducing.
Previously copying devices have been employed for the production of such color copies and reproduction cameras have been utilized for the production of high quality copying masters and the original masters being respectively transferred as a whole to the color material For the purpose of simple color correction in the case of color copies, color filters are introduced into the exposure path so as for example to compensate the overall color cast of an original master. Contrast and color correction masks must be produced and interposed into the exposure path so as to achieve a higher quality color correction in the case of copy masters Enlargement cameras are also employed so as to bring the original masters to the final format. Complicated intermediate processes have been required for producing copy masters in the prior art.
The prior art methods for producing color images have the disadvantage that due to the additional production of correction masks and intermediate negatives, the methods are complicated and time consuming and expensive and do not enable optimum color correction. Also, a loss of sharpness can occur when a specific copy master is enlarged relative to the original master.